Engine cooling system

ABSTRACT

An engine cooling system may include a first water jacket provided in a cylinder block; a second water jacket provided in a cylinder head; a main line connected to a water pump, the first water jacket, the second water jacket, and a radiator such that a coolant discharged from the water pump passes through the first water jacket and the second water jacket to be circulated to the water pump via the radiator; the third water jacket provided in a cylinder separately from the first water jacket or the second water jacket; and a sub-line connected to the water pump and the third water jacket such that the coolant discharged from the water pump passes through the third water jacket to be directly circulated to the water pump without passing through the radiator.

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No. 10-2018-0111038, filed Sep. 17, 2018, the entire contents of which is incorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates generally to an engine cooling system and, more particularly, to an engine cooling system for increasing the temperature rise rate of an engine.

Description of Related Art

As well known in the art, heat generated in a combustion chamber of an internal combustion engine is transferred to a cylinder head, a cylinder block, intake and exhaust valves, and a piston. If the temperature of these engine components excessively rises, heat distortion occurs or the lubricating-oil film on the cylinder wall is broken down, causing a lubrication failure to occur leading to thermal problems of the engine.

Additionally, such thermal problems of the engine may cause abnormal combustion such as combustion failure, engine knocking, and the like to occur, leading to serious damage such as corrosion of the piston and the like and leading to a reduction in thermal efficiency and output. Thus, a cooling system for cooling the engine by circulating a coolant has been applied to prevent the temperature of each component of the engine from rising excessively.

FIG. 1 is a view showing a configuration of an engine cooling system according to the related art.

Referring to FIG. 1, the engine cooling system according to the related art is configured such that a coolant supplied from a water pump 20 forcing the coolant to circulate is supplied to water jacket 30 and water jacket 40 having water jackets 41 and 42 respectively provided in a cylinder block 11 and a cylinder head of an engine 10. The coolant flowing through the water jackets 30 and 40 cools the surrounding metal surfaces that correspond to a combustion chamber.

The coolant having passed through the cylinder block 11 and the cylinder head 12 may branch to pass through a radiator 60 or may bypass the radiator 60 to be circulated to the water pump 20. The radiator 60 may be further provided with a thermostat 70 such that the coolant is controlled to pass through or bypass the radiator 60 according to the temperature of the coolant.

Meanwhile, excessive cooling of the engine 10 causes problems such as deterioration in engine output and fuel mileage, low temperature wear of the cylinder, and the like, so that the temperature of the coolant for cooling the engine 10 is controlled to be maintained at an appropriate level. In other words, when the temperature of the coolant for cooling the engine 10 is low, such as in a warm-up condition of the engine 10, it is required to rapidly raise the temperature of the coolant.

The information included in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and may not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing an engine cooling system including a sub-line and an additional water jacket that cools a cylinder of an engine, making it possible to rapidly raise the temperature of a coolant when it is required to raise the temperature of the engine.

According to various aspects of the present invention, there is provided an engine cooling system, including: a first water jacket provided in a cylinder block; a second water jacket provided in a cylinder head; a main line connected to a water pump, the first water jacket, the second water jacket, and a radiator such that a coolant discharged from the water pump passes through the first water jacket and the second water jacket to be circulated to the water pump via the radiator; the third water jacket provided in a cylinder separately from the first water jacket or the second water jacket; and a sub-line connected to the water pump and the third water jacket such that the coolant discharged from the water pump passes through the third water jacket to be directly circulated to the water pump without passing through the radiator.

The third water jacket may be positioned on an exhaust side in the cylinder head, causing the coolant flowing into the third water jacket to be heated by exhaust gas.

The engine cooling system may further include: a bypass line connected to allow the coolant having passed through the first water jacket and the second water jacket to bypass the radiator and thus to be directly circulated to the water pump; and a thermostat positioned at a point where the bypass line branches from the main line and controlling flow of the coolant based on temperature of the coolant.

The sub-line may be connected to an exhaust gas recirculation (EGR) cooler or heater at a position between the third water jacket and the water pump such that the coolant having passed through the third water jacket passes through the EGR cooler or heater prior to being circulated to the water pump.

The engine cooling system may further include: a first valve positioned at a point where the main line and the sub-line branch from the water pump and controlling flow of the coolant supplied to each of the main line and the sub-line; and a controller configured for controlling a flow rate of the coolant supplied to each of the main line and the sub-line by controlling an opening ratio of the first valve based in a state of an engine.

When temperature of the engine is required to be increased, the controller controls the opening ratio of the first valve to increase the flow rate of the coolant supplied to the sub-line.

The engine cooling system may further include: a connection line branching from the sub-line to be connected to the main line; a second valve positioned at a point where the connection line branches from the sub-line and controlling flow of the coolant supplied to the sub-line; and a controller configured for controlling an opening ratio of the second valve based on temperature of the coolant and thus controlling a flow rate of the coolant supplied to the main line through the connection line after having passed through the third water jacket through the sub-line.

When the temperature of the coolant is equal to or less than a predetermined temperature, the controller may be configured to control the opening ratio of the second valve to block the coolant supplied from the sub-line to the main line through the connection line.

According to the engine cooling system according to an exemplary embodiment of the present invention, provision of the additional water jacket makes it possible to rapidly raise the temperature of the coolant.

Furthermore, circulating the coolant through the sub-line having a relatively short path leads to a reduction in flow resistance, making it possible to enable the coolant to be circulated more rapidly and thus achieve an increase in the temperature rise rate.

Furthermore, it is possible to rapidly raise the temperature of the low-temperature engine, leading to an improvement of engine output and fuel mileage while preventing low temperature wear of the cylinder.

The methods and apparatuses of the present invention have other features and advantages which will be apparent from or are set forth in more detail in the accompanying drawings, which are incorporated herein, and the following Detailed Description, which together serve to explain certain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view showing a configuration of an engine cooling system according to the related art;

FIG. 2 is a block diagram showing an engine cooling system according to an exemplary embodiment of the present invention; and

FIG. 3 is a view showing a first water jacket, a second water jacket, and a third water jacket of the engine cooling system according to the exemplary embodiment of the present invention.

It may be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various features illustrative of the basic principles of the present invention. The specific design features of the present invention as included herein, including, for example, specific dimensions, orientations, locations, and shapes will be determined in part by the particularly intended application and use environment.

In the figures, reference numbers refer to the same or equivalent parts of the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the present invention(s) will be described in conjunction with exemplary embodiments of the present invention, it will be understood that the present description is not intended to limit the present invention(s) to those exemplary embodiments. On the other hand, the present invention(s) is/are intended to cover not only the exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the present invention as defined by the appended claims.

Specific structural and functional descriptions of embodiments of the present invention included herein are only for illustrative purposes of the exemplary embodiments of the present invention. The present invention may be embodied in various forms without departing from the spirit and significant characteristics of the present invention. Therefore, the exemplary embodiments of the present invention are included only for illustrative purposes and may not be construed as limiting the present invention.

Reference will now be made in detail to various embodiments of the present invention, specific examples of which are illustrated in the accompanying drawings and described below, since the exemplary embodiments of the present invention may be variously modified in various forms. While the present invention will be described in conjunction with exemplary embodiments thereof, it is to be understood that the present description is not intended to limit the present invention to those exemplary embodiments. On the other hand, the present invention is directed to cover not only the exemplary embodiments of the present invention, but also various alternatives, modifications, equivalents and other embodiments which may be included within the spirit and scope of the present invention as defined by the appended claims.

It will be understood that, although the terms “first”, “second”, etc. may be used herein to describe various elements, these elements may not be limited by these terms. These terms are only used to distinguish one element from another element. For instance, a first element discussed below may be termed a second element without departing from the teachings of the present invention. Similarly, the second element may also be termed the first element.

It will be understood that when an element is referred to as being “coupled” or “connected” to another element, it may be directly coupled or connected to the other element or intervening elements may be present therebetween. In contrast, it may be understood that when an element is referred to as being “directly coupled” or “directly connected” to another element, there are no intervening elements present. Other expressions that explain the relationship between elements, such as “between”, “directly between”, “adjacent to”, or “directly adjacent to” may be construed in the same way.

The terminology used herein is for describing various exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise”, “include”, “have”, etc. When used in the present embodiment, specify the presence of stated features, integers, steps, operations, elements, components, and/or combinations thereof but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or combinations thereof.

Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. It will be further understood that terms used herein should be interpreted as having a meaning which is consistent with their meaning in the context of the present specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Hereinbelow, various exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Throughout the drawings, the same reference numerals will refer to the same or like parts.

FIG. 2 is a view showing a configuration of an engine cooling system according to an exemplary embodiment of the present invention, and FIG. 3 is a view showing a first water jacket 30, a second water jacket 40, and a third water jacket 50 of the engine cooling system according to the exemplary embodiment of the present invention.

Referring to FIG. 2 and FIG. 3, the engine cooling system according to the exemplary embodiment of the present invention includes: a first water jacket 30 provided in a cylinder block 11; a second water jacket 40 provided in a cylinder head 12; a main line 110 connected to a water pump 20, the first water jacket 30, the second water jacket 40, and a radiator 60 such that a coolant discharged from the water pump 20 passes through the first water jacket 30 and the second water jacket 40 to be circulated to the water pump 20 via the radiator 60; the third water jacket 50 provided in a cylinder separately from the first water jacket 30 or the second water jacket 40; and a sub-line 100 connected to the water pump 20 and the third water jacket 50 such that the coolant discharged from the water pump 20 passes through the third water jacket 50 to be directly circulated to the water pump 20 without passing through the radiator 60.

An engine 10 includes the cylinder block 11 having a cylinder therein and a cylinder head 12 mounted on the top portion of the cylinder block 11 to define the ceiling of the cylinder. Both the cylinder block 11 and the cylinder head 12 may withstand the pressure and temperature due to combustion. To the present end, the first and second water jackets 30 and 40 are respectively provided in the cylinder block 11 and the cylinder head 12 to cause the coolant to be circulated for cooling.

The engine cooling system according to the exemplary embodiment of the present invention includes the first water jacket 30 and the second water jacket 40 respectively provided in the cylinder block 11 and the cylinder head 12 of the engine 10. The water pump 20 provides power to pump the coolant to force the coolant to circulate when the engine 10 is driven.

The cylinder head 12 is a portion where a large amount of heat is generated when a combustion reaction occurs in the cylinder of the engine 10. The second water jacket 40 may have a segmented structure of water jackets 41 and 42 segmentally cooling upper and lower portions of the cylinder head 12. Furthermore, the cylinder head 12 may have an integrated structure of the upper and lower portions.

The cylinder block 11 may further include an oil cooler 13 cooling oil supplied to the engine 10, the oil cooler being connected to the first water jacket 30 such that the oil cooler 13 and the first water jacket 30 are sequentially disposed.

The main line 110 is connected to the water pump 20, the first water jacket 30, the second water jacket 40, and the radiator 60 such that the coolant discharged from the water pump 20 passes through the first water jacket 30 and the second water jacket 40 to be circulated to the water pump 20 via the radiator 60.

The coolant having been discharged from the water pump 20 sequentially passes through the first water jacket 30 and the second water jacket 40 to sequentially cool the cylinder block 11 and the cylinder head 12. The radiator 60 is provided at a position between the second water jacket 40 and the water pump 20. Accordingly, the coolant discharged from the second water jacket 40 is circulated to the water pump 20 through the main line 110 via the radiator 60.

The third water jacket 50 may be provided in the cylinder separately from the first water jacket 30 or the second water jacket 40. The sub-line 100 is connected to the water pump 20 and the third water jacket 50 to provide connection between the water pump 20 and the third water jacket 50. This causes the coolant discharged from the water pump 20 to pass through the third water jacket 50 and causes the coolant having passed through the third water jacket 50 to be directly circulated to the water pump 20 without passing through the radiator 60. In other words, the sub-line 100 does not have the radiator 60 separately connected thereto, causing the coolant to be directly circulated to the water pump 20.

Thus, the engine cooling system according to an exemplary embodiment of the present invention are directed to providing an additional water jacket, thus rapidly raising the temperature of the coolant. Furthermore, the engine cooling system according to an exemplary embodiment of the present invention are directed to providing the sub-line 100 having a relatively short path to allow the coolant to be circulated therethrough, leading to a reduction in flow resistance. This makes it possible to enable the coolant to be circulated more rapidly and thus increase the temperature rise rate.

The present invention may further include: a bypass line 120 connected to allow the coolant having passed through the first water jacket 30 and the second water jacket 40 to bypass the radiator 60 and thus to be directly circulated to the water pump 20; and a thermostat 70 positioned at a point where the bypass line 120 branches from the main line 110 and controlling the flow of the coolant based on the temperature of the coolant.

The thermostat 70 is positioned between the first and second water jackets 30 and 40 and the radiator 60 of the main line 110 and controls the flow rate of the coolant flowing into the radiator 60 by causing a valve to transition between opened and closed positions. This enables the coolant to be maintained at an appropriate temperature (for example, in a range of 80 to 90° C.).

Specifically explained, when the temperature of the coolant is equal to or greater than a predetermined temperature, the thermostat 70 causes the coolant to be circulated to the water pump 20 through the main line 110 via the radiator 60. When the temperature of the coolant is less than the predetermined temperature, the thermostat 70 causes the coolant to be directly circulated to the water pump 20 through the bypass line 120 without passing through the radiator 60.

The thermostat 70 may be a mechanical thermostat in which the valve is simply opened or closed in a response to expansion of built-in wax, or may be an electronic thermostat in which the amount of heat of a heater is controlled according to a driving state or load state of a vehicle to control the expansion of the wax, thus controlling an opening ratio of the valve, whereby the flow rate of the coolant flowing through the radiator 60 is controlled and thus the temperature of the coolant is variable controlled.

When the electronic thermostat is used, a temperature sensor or measuring the temperature of the coolant may be positioned together with the thermostat 70.

The third water jacket 50 is positioned on the exhaust side in the cylinder head 12, causing the coolant flowing therein to be heated by exhaust gas. The cylinder head 12 is a portion where a large amount of heat is generated in the cylinder of the engine 10. The exhaust side of the cylinder head 12 is heated by exhaust heat, thus rising in temperature relatively faster than the intake side thereof.

Thus, the third water jacket 50 is mounted on the exhaust side in the cylinder head 12 to be rapidly heated by heat exchange with exhaust gas or the cylinder head 12, making it possible to rapidly raise the temperature of the coolant flowing into the third water jacket 50.

The sub-line 100 may be connected to an exhaust gas recirculation (EGR) cooler or heater 140 at a position between the third water jacket 50 and the water pump 20 such that the coolant having passed through the third water jacket 50 passes through the EGR cooler or heater 140 prior to being circulated to the water pump 20.

The heater 140 may generate heat in an air conditioner or the like to control the vehicle internal temperature. The heater 140 may be connected to the sub-line 100 connected from the third water jacket 50 to the water pump 20 to heat the coolant.

The EGR cooler 140, which is a portion of an exhaust gas recirculation (EGR) device that re-circulates exhaust gas of the engine 10 into intake air of the engine 10, lowers the temperature of EGR gas. The EGR cooler 140 may be configured with a separate water jacket cooling the EGR gas. The EGR cooler 140 heats the coolant therein through heat exchange with the EGR gas.

In other words, the EGR cooler or heater 140 is connected to the sub-line 100 at a position before the coolant is circulated from the third water jacket 50 to the water pump 20 such that the coolant is caused to be heat exchanged with the EGR cooler or heater 140. This makes it possible to further rapidly raise the temperature of the coolant by the EGR cooler or heater 140.

The present invention may further include: a first valve 80 having an actuator and positioned at a point where the main line 110 and the sub-line 100 branch from the water pump 20 and controlling the flow of the coolant supplied to each of the main line 110 and the sub-line 100; and a controller 150 connected to the actuator of the first valve 80 and configured for controlling the flow rate of the coolant supplied to each of the main line 110 and the sub-line 100 by controlling the actuator of the first valve 80 to regulate an opening ratio of the first valve 80 based in a state of the engine 10. Since the actuator of the first valve 80 to regulate an opening ratio of the first valve 80 is generally known, detailed explanation thereof is omitted.

The first valve 80 may be provided at a point where the coolant discharged from the water pump 20 branches to the main line 110 and the sub-line 100. The first valve 80 may be a three-way valve, and the opening ratio of the first valve 80 is controlled to control the flow rate of the coolant supplied to each of the main line 110 and the sub-line 100.

The controller 150 is provided for appropriately controlling the temperature of the coolant, and may be a portion of an electronic control unit (ECU) or a sub-controller.

The controller 150 may be configured to control the opening ratio of the first valve 80 based on the state of the engine 10. Herein, the state of the engine 10 denotes a driving state of the engine 10 or the temperature of the engine 10. The controller 150 may be connected to a temperature sensor or to receive measured temperature information from the temperature sensor.

When it is required to raise the temperature of the engine 10, the controller 150 may control the opening ratio of the first valve 80 to increase the flow rate of the coolant supplied to the sub-line 100. The case where it is required to raise the temperature of the engine 10 may be the case where it is required to raise the temperature of the engine 10 to increase driving efficiency of the engine, for example, upon a cold-start of the engine.

When the engine 10 is in a low temperature state or in an initial driving state of the engine 10, it is possible to control the flow rate of the coolant to be supplied to the sub-line 100 as much as possible. When the engine 10 is fully driven, it is possible to control the flow rate of the coolant to be appropriately supplied to each of the main line 110 and the sub-line 100.

More specifically explained, when the engine 10 is fully driven, it is possible to control the flow rate of the coolant to be supplied to each of the main line 110 and the sub-line 100 based on the temperature of the engine 10, driving RPM of the engine 10, the fuel injection amount, or the like.

Thus, the present invention can control the coolant to be supplied to the sub-line 100 as much as possible in the low temperature state of the engine 10.

The present invention may further include: a connection line 130 branching from the sub-line 100 to be connected to the main line 110; a second valve 90 having an actuator positioned at a point where the connection line 130 branches from the sub-line 100 and controlling the flow of the coolant supplied to the sub-line 100; and a controller 150 configured for controlling the actuator of the second valve 90 to regulate an opening ratio of the second valve 90 based on the temperature of the coolant and thus controlling the flow rate of the coolant supplied to the main line 110 through the connection line 130 after having passed through the third water jacket 50 through the sub-line 100.

Since the actuator of the second valve 90 to regulate an opening ratio of the second valve 90 is generally known, detailed explanation thereof is omitted.

The connection line 130 may connect the sub-line 100 passing through the third water jacket 50 and the main line 110 passing through the first water jacket 30 and the second water jacket 40 to each other. The sub-line 100 passing through only the third water jacket 50 is relatively low in flow resistance. This causes the pressure of the sub-line 100 to be maintained lower than the pressure of the main line 110 passing through the first water jacket 30 and the second water jacket 40. Thus, the connection line 130 allows the coolant to flow from the sub-line 100 passing through the third water jacket 50 to the main line 110 passing through the first water jacket 30 and the second water jacket 40.

The connection line 130 is provided with the second valve 90 having actuator and connected to the controller 150 to control the flow rate of the coolant supplied from the sub-line 100 to the main line 110. Accordingly, when it is required to further lower the temperature of the coolant having passed through the third water jacket 50, the coolant is supplied to the main line 110 to be circulated through the radiator 60. On the other hand, when it is required to further raise the temperature of the coolant having passed through the third water jacket 50, the coolant is circulated through the sub-line 100 having a relatively short flow path and thus having a short circulation cycle.

When the temperature of the coolant is equal to or less than the predetermined temperature, the controller 150 controls the opening ratio of the second valve 90 to block the coolant supplied from the sub-line 100 to the main line 110 through the connection line 130.

The second valve 90 may be provided with a temperature sensor or measuring the temperature of the coolant. In other words, the flow of the coolant between the main line 110 and the sub-line 100 is controlled by use of the temperature of the coolant having passed through the third water jacket 50, whereby it is determined whether the coolant is cooled.

he temperature sensor or may measure the temperature of the coolant having passed through the third water jacket 50, and the controller 150 may compare the temperature of the coolant measured by the temperature sensor with the predetermined temperature. The predetermined temperature may be a temperature for determining whether it is required to raise the temperature of the coolant.

When the temperature of the coolant having passed through the third water jacket 50 is equal to or less than the predetermined temperature, the second valve 90 is controlled to block the flow of the coolant to the connection line 130, thus achieving a quick temperature rise of the coolant. Thus, it is possible to increase the temperature rise rate when it is required to raise the temperature of the coolant.

Furthermore, when the temperature of the coolant is equal to or greater than a predetermined danger temperature, the second valve 90 is opened with a maximum opening ratio to cause the coolant having passed through the third water jacket 50 through the sub-line 100 to be supplied to the main line 110 as much as possible. Thus, the coolant is enabled to be circulated to the water pump 20 through the radiator 60 as much as possible, thus improving the heat radiation effect.

For convenience in explanation and accurate definition in the appended claims, the terms “upper”, “lower”, “inner”, “outer”, “up”, “down”, “upper”, “lower”, “upwards”, “downwards”, “front”, “rear”, “back”, “inside”, “outside”, “inwardly”, “outwardly”, “internal”, “external”, “inner”, “outer”, “forwards”, and “backwards” are used to describe features of the exemplary embodiments with reference to the positions of such features as displayed in the figures.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described to explain certain principles of the present invention and their practical application, to enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the present invention be defined by the Claims appended hereto and their equivalents. 

What is claimed is:
 1. An engine cooling system, comprising: a first water jacket provided in a cylinder block; a second water jacket provided in a cylinder head; a first line connected to a water pump, the first water jacket, the second water jacket, and a radiator, wherein a coolant discharged from the water pump passes through the first water jacket and the second water jacket to be circulated to the water pump via the radiator; a third water jacket provided separately from the first water jacket or the second water jacket; and a second line connected to the water pump and the third water jacket, wherein the coolant discharged from the water pump passes through the third water jacket to be directly circulated to the water pump without passing through the radiator when the coolant is discharged along the second line.
 2. The engine cooling system of claim 1, wherein the third water jacket is positioned on an exhaust side in the cylinder head.
 3. The engine cooling system of claim 1, further including: a bypass line connected to first and second portions of the first line to allow the coolant having passed through the first water jacket and the second water jacket to bypass the radiator and thus to be directly circulated to the water pump; and a thermostat positioned at one of the first and second portions of the first line where the bypass line branches from the first line and controlling flow of the coolant based on temperature of the coolant such that the coolant is controlled to pass through or bypass the radiator according to the temperature of the coolant.
 4. The engine cooling system of claim 1, wherein the second line is connected to an exhaust gas recirculation (EGR) cooler or heater at a position between the third water jacket and the water pump such that the coolant having passed through the third water jacket passes through the EGR cooler or heater prior to being circulated to the water pump.
 5. The engine cooling system of claim 1, further including: a first valve positioned at a point where the first line and the second line branch from the water pump and configured for controlling flow of the coolant supplied to each of the first line and the second line; and a controller connected to the first valve and configured for controlling a flow rate of the coolant supplied to each of the first line and the second line by controlling an opening ratio of the first valve based on a state of an engine.
 6. The engine cooling system of claim 5, wherein the state of the engine includes a driving state of the engine or temperature of the engine.
 7. The engine cooling system of claim 5, wherein, when temperature of the engine is required to be increased, the controller is configured to control the opening ratio of the first valve to increase the flow rate of the coolant supplied to the second line.
 8. The engine cooling system of claim 1, further including: a connection line connected to a third portion of the first line and a fourth portion of the second line; a second valve mounted at the fourth portion where the connection line is connected to the second line and configured for controlling flow of the coolant supplied to each of the connection line and the second line; and a controller connected to the second valve and configured for controlling an opening ratio of the second valve.
 9. The engine cooling system of claim 8, wherein the controller is configured for controlling the opening ratio of the second valve based on temperature of the coolant for controlling a flow rate of the coolant supplied to the first line through the connection line after having passed through the third water jacket through the second line.
 10. The engine cooling system of claim 9, wherein, when the temperature of the coolant is equal to or less than a predetermined temperature, the controller is configured to control the opening ratio of the second valve to block the coolant supplied from the second line to the first line through the connection line.
 11. The engine cooling system of claim 9, wherein, when the temperature of the coolant is greater than a predetermined temperature, the controller is configured to control the opening ratio of the second valve with a maximum opening ratio to supply the coolant having passed through the third water jacket through the second line to the first line. 